<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style>
			div{
				width:100px;
				height:100px;
				background: black;
				/*border-radius:50px;*/
				/*值是50%的时候 会变成圆*/
				border-radius:50%;
			}
		</style>
	</head>
	<body>
		<div></div>
	</body>
</html>
